text:
Was "the right stuff" ever really the right stuff?
In the history of the culture of aviation, to what extent has the popular image of "the right stuff" required of a pilot ever matched the characteristics actually sought in aviation?
In this popular image, the pilot with "the right stuff" is imbued with, amongst other characteristics:

fearlessness
adventure
masculinity
a strong streak of individualism
stubborn single-mindedness
quick-thinking
sexiness
cool
self-sufficiency
a disregard for limits that bind lesser individuals
a distaste for rules
a stronger belief in himself than in authority
a strong intuitive sense of how to deal with problems in the air
... and others corresponding to the picture of the pilot who gets to walk around with a swagger because he deserves it, as vividly described in Tom Wolfe's The Right Stuff, but also represented that way through countless other descriptions and depictions in popular culture.

Hi Daniele, I like the question but it may be not a good fit here, it seems difficult to answer without introducing an opinion. Perhaps there is a way to edit the question and prevent answers driven by opinions.

I'm not qualified to judge sexy in male pilots, but people like Bob Hoover, Tex Anderson, and Chuck Yeager come to mind on the other qualities.

@mins For example, do military aviation training academies (or did they ever, which is my real question, since I doubt they seek them out now) seek out or encourage the swashbuckling adventurers, the so-called alpha males, highly-competitive top-gun achievers? Or have such characteristics never made for a good fit? Whatever the answer, those will be historical facts about aviation training culture and standards, not matters of opinion.

swaggering mavericks are dangerous and successful - I figured out what you meant the second time I read it, but the first time was a little strange

cool, calm, unflappable under pressure, courageous, quick-thinking is the right stuff, has always been and still is (a student pilot that panics easily is unlikely to pass and instructors often throw problems to students to see if they are unflappable under pressure and quick-thinking). On the other hand swaggering is not the right stuff - don't get me wrong, it is in popular imagination because we like to associate "cool", as in cool kids in high school, with cool professions like F1 driver and pilots when what makes them successful is their attention to detail to the point of geekiness

@SteveV. Amazing the difference a comma can make! Thanks.

Question's closed now, but one note: The great thing about the phrase "the right stuff" is that it's tautological. Whoever made the cut would have the right stuff, and those with the right stuff would make the cut. The list of attributes you mention is almost like cold reading, as something will apply to one pilot or another. Hopefully unflappable and quick-thinking is pretty general, but swaggering and sexy? Don't know if someone like Neil Armstrong would've fit that in the classic sense, even though he did have enough right stuff to manually land the Eagle on the Moon with little fuel left

I've rewritten the question. It's asking exactly the same thing, but perhaps it's clearer that this is asking a question about the historical facts of the culture of aviation.

Well, kind of,
The technical portrayal of test pilots in that film received negative reviews with real test pilots.  I know Chuck Yeager did not like his portrayal by Sam Shepherd and director Philip Kaufman, particularly with the NF-104 accident at the end of the film.  While the scene is based on a real accident which Yeager did have, it was part of a scheduled test flight with established test points and not Yeager throwing on a pressure suit and jumping into the cockpit for a joyride with a YOLO type attitude.
Flight test and test pilot work is rigorously planned out, methodically didacted and cogitated, with multiple contingency plans and contingency plans for those if they don’t work.  Long gone are the days where you strapped your little pink fanny into a crate, pushed it off a cliff, and hoped for the best on the way down.  Test pilots and flight test engineers are very bright and methodical people who are intimately familiar with the systems of the aircraft they are flight testing and have spent a great deal of time thinking about all the ways something can go wrong and what they intend to do if they encounter this problem.  Hundreds, if not thousands of hours have been spent in systems and and flight simulation scenarios, not only evaluating these hypotheses, but making detailed plans for their test points they want to evaluate during flight.  Finally the flight testing itself is a slow and methodical affair, slowly and carefully increasing the performance envelope with each flight and thoroughly evaluating and addressing anomalies once encountered before continuing.  As one test pilot once put it, “We try to make flight testing as boring as possible.”
As to being cool, calm, unflappable under pressure, quick thinking and courageous being the defining qualities of 'the right stuff' in a pilot.  I would argue that they ARE useful to a pilot anywhere.  Remember US Airways Flight 1549's Capt Chesley 'Sully' Sullenberger?  That guy was faced with one of the most challenging scenarios out there and was a cool as a refrigerated cucumber throughout.  You may not be exploring and mapping out the absolute edges of an F-35's flight envelope, but those skills can come in handy with any kind of emergency situation which you might face.
Remember there is a difference between these qualities and having hazardous attitudes e.g. anti-authority, machismo, etc.  As Yeager once put it "If you want to grow old as a pilot, you gotta know when to push it and when to back off."  In addition flight test is a considerably different animal than it was back in Yeager's day, thanks in part to Yeager and a few unfortunates who now have a street at Edwards named after them.
Test flying isn't about being taking big risks; its a gradual and methodical process of exploring the flight characteristics of an aircraft and having multiple contingency plans to make it as safe as possible.  In short, good Aeronautical Decision Making really IS 'The Right Stuff'.  Risk takers, the macho guys, or the just plain stupid get weeded out, either by their superiors or by Natural Selection.

As the saying goes, "There are old pilots, and there are bald pilots, but there are no bald bold pilots".

The spelling on that comment makes no sense.  I’m guessing you meant ‘There are old pilots and there are bold pilots, but there are no old, bold pilots’?

@CarloFelicione - It's way funnier the other way though

My dad was an old bald pilot.

Psychologists know that some people are more leaders than others. Case in point: When the ferry Estonia sunk in 1994, some people went down to sit in their cars (because they felt safe there), others just waited for someone to rescue them and only maybe 10% went up to the lifeboats and actively tried to rescue themselves.
Guess which personality type would qualify as test pilots.
While Tom Wolfe exaggerates the typical test pilot into a macho type who is actually not ideally suited to the task, there is some truth in the observation that some people perform far better in stressful and unanticipated situations than others. The leader type likes to think for him/herself and stays level-headed when other types would panic and rely on leaders for direction.

I don't think "leadership" and "cool under stress" are really at all related.  In your example, "cool under stress" people would have tried to rescue themselves, "leaders" would have tried to get other people to do something.  If the leaders were also cool under stress, it might actually be the right thing, but we have lots of real-world examples of leaders reacting badly to stress, and mis-leading their followers.

@jamesqf: You interpret "leaders" wrongly. Focus on the others instead: They prefer to wait for others and follow orders. Would that make them better test pilots?

@Peter Kämpf: I don't think so.  There are really three kinds of personalities here: the leader, who convinces people to follow; the follower, who readily follows anyone acting like a leader; and the individualist, who goes ahead and does what seems sensible regarldess of other people.  From the little I know of what's involved in test-piloting, I doubt that either of the first two would make particularly good test pilots.

@jamesqf, they are totally related. You ain't going to save anybody if you are not "cool under stress". The ability to lead others is just a bonus on top of that, and one that under stress you don't need, because under stress those who panic will follow anybody who seems to know what they are doing.

@Jan Hudec: But my points are 1) you can be cool under stress without being a leader (and vice versa, of course); and 2) leadership does not seem to be a necessary (or even desirable) quality in a test pilot.


text:
Why can't I build an entire jet engine out of carbon fiber?
I noticed that most jet engines are made out of aluminum or metal components. However, carbon fiber has a melting point of 3500 degrees celcius, way above metal or aluminum. So, can I build an entire jet engine out of carbon fiber?

Carbon fibre burns quite easily. So while it melts at a very high temperature, it will not get anywhere close to that temperature under normal atmospheric conditions - you'll just get a lot of expensive carbon dioxide, which doesn't hold shape very well :)

I don't know about you, but I can't build an entire jet engine out of any material.

@immibis hey, all chocolate is always an option.

Now In 2023, I heard they are using carbon fiber blades instead of titanium. latest tech

No, you can not. Carbon fibre composites always contain a matrix component which serves different functionalities, but (in a micro nutshell) bonds and keeps the fibres in place. What you get is a very complex material with lots of lightweight potential, but also very different property profiles compared to metals.
Most matrix materials (thermoset, thermoplastics) will not work up to engine (combustion chamber) temperatures and either degrade/burn or melt/vaporize/burn long before reaching even a meagre few hundred Kelvin (say, 500K). In fact, carbon fibres will not work as well in an oxygenated high-temperature environment, and degrade/burn up as well.
One composite material that works and is used already in engines are ceramic matrix composites, like (amongst others) e.g. C/C-SiC structures, but those are very special animals (and even there the carbon fibre parts are susceptible to burn). Especially in terms of mechanical properties, these cannot compete with superalloys.
But also for many other, ambient temperature parts, metals are much better suited. Think of example of a ball bearing - doing that completely in composite will not work really well (if at all).

So the engine itself would burn up as fuel for the engine? "You see Ivan..."

@corsiKa lol -  I forgot a suitable preamble: No you can not...  lest you be fond of self-devouring turbmachinery with a dangerous taste for spontaneous, violent and messy disintegration.

You assume you MUST run a jet engine at temperatures above the decomposition temperature of the carbon composite. Although that is not true, one normally endeavors to maintain a high combustion temperature due to thermodynamic efficiency.

@Aron to be sure, I am presuming good-ole fashioned combustion. Anyway, if nit-picking, the question is even only asking about carbon fibres (not composites), so the answer to that is definitely no (unless you invent a turbomachine hammock or self-propelling carpet), but I added some common-sense assumptions.

What is relevant is not the melting point, but the temperature at which the material loses its mechanical properties (such as stiffness or elasticity).
The epoxy (the material keeping together the fibers) will usually degrade much sooner than the fibers, basically voiding the benefit of the material.
There are studies to increase the resistance to high temperatures, but I have no idea how near we are to see them applied to critical components such as the engines.
Also note that usually the blades of the turbine and the combustion chambers are made of alloys designed specifically to resist the high temperatures in those areas of the engines.

Actually, Epoxy as a thermoset will not melt, but degrade / crumble / burn above its maximal operating temperature, although the overall effect is the same: loss of function/stability.

When I was beginning my university studies in engineering 15 years ago our professor told us that they actually think of building jet engines of that material!
Carbon-based materials seem to be the perfect material for jet engines in nearly all points (heat resistance, mechanical strength at high temperatures, weight, ...) with one important exception:
These materials burn when they get in contact with hot air!
The professor told us that a lot of effort and money is spent in search of a coat or varnish that would protect carbon-based parts from the hot air. He told us that jet engines would be built of that material if such a coat is found.
He also told us that up to then no suitable coat was found - obviously this has not changed in the last 15 years.

Interesting, so why doesnt a normal flame retardent coat work on carbon fiber?

If your question is why some carbon fiber material does not burn down when it gets in contact with a burning piece of paper: It can! Some schoolmate accidentally threw some burning paper into a bottle bank made of carbon fiber and it burned down... However our professor told us that the main problem is the temperature difference. Finding some coat that works at high temperatures seems not the problem but the coating must ahere when the engine is heating up or cooling down...

@eli A normal flame retardant will probably itself not survive the temperatures in a jet engine core. In general, assume that nothing is 'normal' when discussing jet engines.

@reirab lol, good advice

@reirab A metalized spray coating?

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
What does a jet engine technician do?
I know that they repair everything that concerns engines, but what is the actual day for them. Do they sit in the factories or work in airports?

@mins After years of training, this guy has the technique down

@mins Fortunately, as bad as that looks, that guy was not seriously injured. Apparently a strap caught on something before he reached the fan.

@TomMcW: Ah that's indeed completely different :) Lucky man!

You ask a very broad question. Jet engine technicians can work in various capacities depending on the job they are hired to do.
In my experience, I worked on the flight-line directly on aircraft removing/installing, performing operational checks, troubleshooting and servicing engines and other systems.
Some technicians work on engines out of the aircraft and in a controlled environment like the factories where engines are made. Others work in repair shops tearing down and rebuilding existing engines.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What difference is there between stabilizers and stabilators concerning longitudinal stability?
It is known how stabilizers affect the longitudinal stability of an airplane.
What about longitudinal stability in airplanes using stabilators (all-flying tails) or trimmable stabilizers?
Is it to be expected that certain combinations of angles of attack of the main wing and stabilators or trimmable stabilizers should lead to longitudinal instabilities?

Stabilizers, in this case, means the whole thing including the control surface, whatever that control surface is.

There is no fundamental difference between them in such context. If you don't go to the extremes like 90° deflection (and generally stay in the linear range), you can mentally replace an elevator with a stabilator at a different equivalent angle. All-moving surfaces are typically a design solution when additional efficiency is required for whatever reason.
There are finer effects, especially at supersonic, but they don't change the overall picture for 'normal' aircraft. You can always find border cases when, say, elevator will stall but an equivalent stabilator will not yet, but they will generally be beyond the operational envelope.
Stability is primarily determined by derivatives, i.e. the way moments change with changing angles (of attack in this case). Absolute angles (tail vs wing) are less important and are usually the consequence of the desired derivatives.

I actually thought about static stability. I can imagine some situations when an angle of attack combination of main wing and stabilator (the all-moving part used to control the airplane) could lead to a static longitudinal instability. Static longitudinal stability is also determined by the angle of attack difference of main wing and stabilizer (the non-moving part used for static longitudinal stability). I expect this has to be considered when using stabilators. I agree with you that a stabilator could be approximated by a stabilizer in order to estimate it.

What I mean by this is the following: Not the whole deflection range of a stabilator is allowed in the whole angle of attack range of the main wing (and following from this also e.g. the whole airspeed range when in level flight). Otherwise this would lead to loss of static longitudinal instability.


text:
What is the maximum theoretical lift of a plane as a function of engine power and surface of the wings?
Maximum theoretical lift of a plane as a function of engine power and surface of the wings?
I know that the maximum static thrust of a propeller turned by an engine of power $P$ can not be greater than:
$$Thrust_{max}=\sqrt[3]{2\pi(\frac{D}{2})^2 \rho P^2}$$
where $\rho$ is the density of the air and $D$ the diameter of the propeller.
I am looking for a formula that gives the maximum theoretical lift of a plane which flies horizontally. After half a page of demonstrations I have found a relation:
$$Lift_{max}=\sqrt[3]{2S \rho P^2}$$
but I am not sure if it is correct ($S$ is the total surface of the wings).
Update 1
Two examples that show the formula for max lift gives lifts smaller than the loaded weight of the plane. I do not know why.
1) Cessna 172: Gross weight - $1,111kg$, Powerplant - $160 hp$, Wing area - $16.2 m^2$
$Lift_{max}=(2 * 16.2 m^2 * 1.2 kg/m^3 * (160 hp)^2)^{1/3}=837 kgf<1,111kgf$
2) de Havilland DHC-6 100 Twin Otter: Gross weight - $5,246kg$, Powerplant - $2*579 eshp$, Wing area - $39 m^2$
$Lift_{max}=(2 * 39 m^2 * 1.2 kg/m^3 * (2 * 579 hp)^2)^{1/3} = 4,198 kgf<5,246kgf$
Update 2
I have tried a different demonstration that stars from the known relations:
$$Lift={0.5 \rho S C_L V^2}$$
$$Drag={0.5 \rho S C_D V^2}$$
$$Power=Drag * V$$
By eliminating the speed of the plane, $V$, the lift result as being:
$$Lift = \sqrt[3]{2S \rho P^2 \frac{C_L^3}{4 C_D^2}}$$
It appears that this new lift can be greater than $\sqrt[3]{2S \rho P^2}$ as long as $\frac{C_L^3}{4 C_D^2}$ does not seem to be restricted to always remain less than 1.
Update 3
Using the formulas for $C_D$ an $L_{max}$, suggested to me by Peter Kampf and mnunos, I have made some evaluations.
$$C_D = C_{D0} + \frac{C_L^2}{\pi\cdot AR\cdot\epsilon}$$
$$L_{max}=\frac{1}{2}\cdot \sqrt{3\pi AR\epsilon}\cdot \sqrt[3]{\frac{P^2\eta^2\rho S}{4 \sqrt{C_{D0}}}}$$
For the assumed values: $\eta=0.7$, $\epsilon=0.8$, $C_{D0}=0.03$, $\rho=1.2\: kg/m^3$ and the data taken from the Cessna 172 general characteristics: $P = 160\:hp$, $S=16.2\:m^2$ and $AR=7.32$, I get:
$$L_{max,\:\eta=0.7}=2199\:kgf$$
However, only $57.451\:hp$ are necessary for lifting $1111\:kg$ (horizontal flight), the rest up to $160\:hp$ can be used for climbing.
From the relation:
$$m_{plane}gV_{climb} = \eta(160\:hp - 57.451\:hp)$$
I get $V_{climb}= 4.913\:m/s$ which is significantly greater than the rate of climb 3.66 m/s the Cessna 172 has.
It seems that working with $C_{D0}$ and $\epsilon$ gives only a quite rough estimate of the max lift. Without knowing the actual $C_L=C_L(C_D)$ little can be said about the real maximum possible lift of a certain plane.
Update 4
The maximum theoretical thrust of an ideal helicopter propeller having the diameter identical to the wingspan, $11\:m$,  of a Cessna 172:
$$T_{max,Diameter\:prop=11\:m}=(2 * pi * (11 m / 2)^2 * 1.2 kg/m^3 * (160 hp)^2)^{1/3} = 1 509.95\:kgf$$
is considerably smaller than the max lift of the plane,  $L_{max,\:\eta=0.7}=2199\:kgf$, I calculated in Update 3. Is such a result logical?  Does it have an explanation?

Shouldn't the theoretical L/D max ratio of the wing be taken into consideration in the second equation? In turn L/D max depends on the Reynolds number, hence on the assumed speed.

The problem is that I only know the total surface of the wings and the power of the engine. The ratio L/D and the speed are unknown in my case. The max thrust for a propeller, which is a wing that rotates so it generates lift and drag, is calculated using the momentul theory (see: https://en.wikipedia.org/wiki/Momentum_theory), a procedure that does not make use of CD and CL. I applied the same method for evaluating the max lift of a plane.

I'm not an aerodynamics expert, but one of the pre-requisites of the MT is that "Viscous effects are not considered (no drag, no momentum diffusion)". That doesn't seem to match the wing conditions. There are a bunch of formulas in this summary, in case you can do something with them.

It appears that if Drag and other losses are taken into account a part of the available power P is dissipated without producing any lift. In consequence, the real lift should be smaller than what I calculated. However, after testing the formula on a few planes, the max possible lift I get is, in many cases, smaller than the weight of the plane which is an incorrect result. I will update the question with more explanations.

I think the main problem is that you're using horsepower, while all the other units are in SI. If you substitute 746 W = 1hp, your answers might make more sense

I do not do the calculations by hand. I simply copy in the Google Search Box strings like this (2 * 39 m^2 * 1.2 kg/m^3 * (2 * 579 hp)^2)^(1/3) = kgf (you can try by yourself) and Google performs automatically all the necessary conversions and displays the correct result.

....and now @Peter Kampf is going to fly in like and angel and solve all your troubles magically. :)

Your thrust equation is only valid for the static case (initial speed at infinite distance from the propeller is zero), and neglects the propeller's efficiency. For the flight case, I recommend to make a bold assumption for propeller efficiency and to assume that most power will be converted to thrust:
$$T = \frac{P}{v}\cdot\eta_{Prop}$$
A large, slowly turning propeller will have an efficiency approaching 90%, while a small, fast-spinning one will only reach 70%. If operated outside of its design speed, efficiency might even become negative. If you look for an upper boundary of thrust, the equation above sans efficiency will do nicely.
For the maximum lift answer you should expand your drag coefficient a little, as recommended already in this answer. $$c_D = c_{D0} + \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$$
Now you can equate drag and thrust to get: $$P\cdot\eta_{Prop} = \left(c_{D0} + \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}\right)\cdot S\cdot\frac{\rho}{2}\cdot v^3$$
and solve for lift: $$L = c_L\cdot S\cdot\frac{\rho}{2}\cdot v^2 = \sqrt{\pi\cdot AR\cdot\epsilon\cdot\left(\frac{P}{v}\cdot\eta_{Prop} - c_{D0}\cdot S\cdot\frac{\rho}{2}\cdot v^2\right)}\cdot\sqrt{S\cdot\frac{\rho}{2}\cdot v^2}$$
The minimum power is consumed when the ratio $\frac{c_L^3}{c_D^2}$ reaches its maximum. Expressed differently, this means that $$c_L = \sqrt{3\cdot\pi\cdot AR\cdot\epsilon\cdot c_{D0}}$$
Plugging that back into the lift equation I leave as an exercise to the reader.
As you can see, the answer really depends on the aerodynamic quality of your airfoil. The best you can reach with regular airfoils is a $c_L$ between 1.5 and 1.8, depending on Reynolds number. With slotted flaps this can be doubled, but $c_{D0}$ will go up substantially, so the best ratio $\frac{c_L^3}{c_D^2}$ can be gained with a clean airfoil.
Nomenclature:
    $c_L \:\:\:$ lift coefficient (normally between 0 and 1.5)
    $S \:\:\:\:\:$ Wing surface area
    $\pi \:\:\:\:\:$  3.14159$\dots$
    $AR \:\:$  aspect ratio of the wing (ratio of span to mean chord)
    $\epsilon \:\:\:\:\:$  the wing's Oswald factor (use 0.8 when in doubt)
    $c_{D0} \:$  zero-lift drag coefficient (use 0.02 when in doubt and 0.03 with a fixed gear)

In the case of Cessna 172, using 0.8 for the Oswald factor and 0.3 for the zero-lift drag coefficient and considering the efficiency of the propeller as being 70%, I get a max lift that is more than double the gross weight of the plane which is 1111 kg. Is such a result realistic?

@RobertWerner: First of all, it should be 0. 0 3 for the zero-lift drag and yes, the maximum lift must be more than the weight in order to have reserves for turns. Real lift almost never is close to maximum lift, but is what is needed to stay aloft.

I made the calculations with 0.03. By mistake I wrote 0.3 in my previous comment. I get $L_{max100}$ = 2790 kgf for the theoretical case when the efficiency is 100% and $L_{max60}$ = 1984 kgf for $\eta=$ 60%. It appears that even for a quite low efficiency like 0.6 there is a huge surplus of lift 1984 - 1111 = 873 kgf that seems unrealistic. I will update the initial question to further explain way.

@RobertWerner: Which power setting did you use? Piston engines are rarely used at their full rated power; something around 70% is more likely for continuous use.

I used the power specified in the general characteristics of Cessna 172: Powerplant: 1 × Lycoming IO-360-L2A four cylinder, horizontally opposed aircraft engine, 160 hp (120 kW). I calculated that Cessna 172 can climb at its specified 3.66 m/s if the engine delivers only $0.745*160:hp$ and a propeller 70% efficient is utilized. I have to verify if that 3.66 m/s really corresponds to using only around 75% of the engine power. This should be written somewhere.

I got a result that puzzled me. See Update 4 of my initial question.

Try to write down  step by step how did you get your first formula for $Lift_{max}$. Check not only the math but also the physical meaning of each formula and you'll probably find the error.
If you want to calculate the maximum possible lift of an airplane for a given geometry you need to know its lift and drag polars as you wrote in the second update.
Starting with the lift formula in the second update,
$$L=\sqrt[3]{\frac{S\rho P^2}{2}\cdot \frac{C_L^3}{C_D^2}}$$
and assuming a quadratic function for the drag,
$$C_D=C_{D0}+k \cdot C_L^2$$
we can maximize L:
$$\frac{\partial L}{\partial C_L}=0 \implies \frac{\partial}{\partial C_L}(\frac{C_L^3}{(C_{D0}+k \cdot C_L^2)^2})=0 \implies C_{L,Lmax}=\sqrt{\frac{3C_{D0}}{k}}$$
Substituting $C_L$ with your calculated $C_{L,Lmax}$ we get an expression for the maximum lift:
$$L_{max}=\frac{1}{2}\cdot \sqrt{\frac{3}{k}}\cdot \sqrt[3]{\frac{P_{t}^2\eta^2\rho S}{4 \sqrt{C_{D0}}}}$$
I also substituted $P=P_{t}\cdot \eta$. $\eta$ is the thrust efficiency due to losses in the gear, propeller,...
Now lets see if it makes qualitatively sense:

$\downarrow k$ and $\downarrow C_{D0} \implies \uparrow L_{max}$
$\uparrow P_t$ and $\eta \implies \uparrow L_{max}$

This seems to be OK. Now let us calculate some values.
Using $T\cdot V=\eta P_t$ and $T=D=C_D\frac{\rho}{2}V^2$ we get the velocity we are flying at:
$$V=\sqrt[3]{\frac{2P_t\eta}{C_D S \rho}}\\
\implies V_{Lmax}=\frac{1}{\sqrt[3]{2}}\cdot\sqrt[3]{\frac{P_t\eta}{C_{D0} S \rho}}$$
For comparision we can also calculate this values for $L/D_{max}$, the best glide point:
$$\frac{\partial L/D}{\partial C_L}=0 \implies \frac{\partial}{\partial C_L}(\frac{C_L}{C_{D0}+k \cdot C_L^2})=0 \implies C_{L/Dmax}=\sqrt{\frac{C_{D0}}{k}} \\
\implies V_{L/Dmax}=\sqrt[3]{\frac{P_t\eta}{C_{D0} S \rho}}$$
The relationship between the velocities at the best glide and maximum lift point is:
$$\frac{V_{Lmax}}{V_{L/Dmax}}=\frac{1}{\sqrt[3]{2}}\approx 0.79$$
If we look at a Cessna 172 we get:
 $$\frac{V_x}{V_{bg}}\approx \frac{60 KCAS}{73 KCAS}=0.82$$
This is close to the theoretical value we had calculated. (I have assumed that flying with best climb angle speed is also flying with maximum lift.)

(source: fiu.edu)
Drag, and thrust of a Cessna 172. Picture source
While I do not have exact values for the Cessna, for $\eta=0.4$, $k=0.04$ and $C_{D0}=0.03$ at sea level I get $L_{max}\approx 17600 N$, which is also a plausible result. Therefore I suppose that the formula for $L_{max}$ is correct.

The formula of the max lift, you obtained, appears to be correct and quite useful for me. A question, why did you take the efficiency so low, 40%?

@RobertWerner Because the pilot forgot to clean the dead flies on the propeller and after thirty years the motor isn't so powerful anymore... It's the only value I didn't think much about. Take a higher efficiency if you want. To calculate $k$ and $C_{D0}$ I used the first polar with measured values I found in Google-images.

@RobertWerner I don't have enough reputation to answer on the other comment, but assuming a you get a maximum lift twice the weight you would have half of your power available for climb. With $G=10900N$, $P=120kW$ and $\eta=0.7$ you get $G\cdot V_{climb}=P\cdot \eta\cdot 0.5 \implies V_{climb}= 3.85m/s$. This is a quite accurate estimation of real climb speeds.

For $\eta=$ 70% I get $V_{climb}$ = 4.9 m/s. I will update the question to explain why.


text:
Why don't airport have heated runways to deal with winter conditions?
It is for years that I ask myself as a frequent flyer why there is no Airport using a system, like built-in electrical resistances on Runways to avoid Delays/Cancellations and even closing Airfields during winter? The costs of such a system would be for sure less than closing an Airfield for one day.

Please specify for what temp and precipitation ranges you want the system to work. Please also consider how you are going to drain thawed water, unclog the drainage, check if the rwy is clear of ice and snowdrifts, and repair it in a snowstorm.

The costs of such a system would be for sure less than closing an Airfield for one day.  How confident are you of that statement?  I am far from confident.  Install it, maintain it for the 5 days in 365 you actually need it, then supply it with enough electricity to heat an entire runway?  I am far from convinced that it would be anywhere near cheaper.

Melting snow requires HUGE amounts of electricity. See https://what-if.xkcd.com/130/ for reference

Removing snow from runways is not the biggest problem. Snow can be ploughed from the runways pretty quickly. The problems occur:

When it is snowing, especially in snow storms with strong winds and poor visibility. The wind and visibility are bigger problem than the snow laying on the runway and when the snow fall rate is such that the snow becomes a problem itself, the heating system would not be able to keep up melting it anyway.
Due to snow and ice accumulating on aircraft preparing for take-off. Obviously heating runways would not help in this regard.
Due to fog, which is much more common in winter. Again, heating runways would not help in this regard.

So runway heating would probably not help very often.
Also the runway has to be extremely strong, because aircraft have much higher weight on each tire than cars. A heating system with adequate durability would therefore be really expensive.

Do they use salt/sand on runways like they do on streets?

@TomMcW http://aviation.stackexchange.com/questions/9436/what-do-they-use-to-de-ice-aircraft-and-runways-on-snowy-days

I don't know how to calculate it, but I am sure that heating a runway will use a lot of electricity. Imagine yourself on that runway with a 2Kw electric fire in snowy conditions. You would still be freezing, and the fire would have no effect on the runway surface. Even if you could do this, the heating might create fog above the runway.
I don't think runway conditions are the biggest problem in winter, because as long as it isn't snowing continuously, snow ploughs can clear a runway (salt isn't used because it would be damaging/corrosive to aircraft).
The problems in winter often are the other weather conditions such as strong crosswinds, poor visibility, low cloud base, because unless AutoLand is being used (available only on some aircraft/some airports), the pilot generally has to be able to see the runway when coming into land from an height typically of 200 feet.

Good point. How did I only forgot? Yes, it takes awful lot of energy. Specific heat of melting of water is ~335 kJ/kg. 1 mm of precipitation means 1 kg per square metre, but snow has a lot of air in it, so it corresponds to 10-20 mm (so say 1 cm). Now for stronger snowing 20 cm/hour is possible and to melt that much, we'd need ~ 1.9 kW/m². Now a runway at larger airport may have, say, 160 000 m² and we are at about 300 MW. That's in the same ballpark as this snow-melting XKCD What If.

Typical runway at a major hub is at least 150ft x 10,000ft and could be as large as say 200ft x 16,000ft.  That gives areas for a single runway of 140,000 to 300,000 m^2.  And that's just ONE runway; some hubs have as many as 10 runways!  And it doesn't even count taxiways, parking aprons, freight ramps, emergency areas, runup pads, etc.  Too bad Solar Freakin' Roadways are impractical!

"I don't know how to calculate it, but I am sure that heating a runway will use a lot of electricity." The formulas are included in AC 150_5370_17 - Heated pavement systems, and other possible sources include geothermal waters, waste combustion or heat pump (which uses electricity, but extracts more energy from the ground).

It seems to have been done on runways, taxiways and parking stands, though not by using electric resistors, as you suggest. See the following articles from the interwebz:

Interseasonal Heat Transfer implemented by the company ICAX in Toddington.
Heated runway concept trials, funded by the FAA. This includes a portion of a taxiway at O'Hare.

There's a pretty important quote in the FAA article: "Airport officials remain generally opposed to the concept of heated runways because of the high energy costs.  'There isn't a compelling need for these systems in the industry,' said Chris Oswald."

This "answer" should be improved, as it is the reader needs to read several pages of text, and ends up with an unclear view of whether heating a runway is realistic.


text:
What are outer marker horizontal dimensions at 3 degrees ILS path?
What is the outer marker "distance" along the flight path of a 3 degree ILS?
I provide my two approaches below, but as they contradict each other, I am asking this question to learn the proper answer.
Approach #1: Wikipedia says OM horizontal dimensions is an ellpsoid of 2400 x 4200 ft (I assume the former is the dimension parallel to aircraft's path ) at 1000 ft. I assume vertically OM signal is of conical shape, therefore its horizontal size expands and should be (proportionally) larger at higher altitudes. At 3 degree glideslope, altitude range for OM crossing is between 1200 and 2100 ft (4 NM and 7 NM respectively). This gives an answer to my question equal to a range between 2400 * 1.2 = 2880 and 2400 * 2.1 = 5040 ft.
Approach #2: Flying at 100 kts, I can hear OM for ca. 12 seconds at 4.4 DME. This translates to 2000 ft of OM length at height of 1500 ft. Empiria does not give a range, but still contradicts wikipedia and is much more reasonable number, as I cannot remember hearing OM for almost half a minute while flying over...

While the ideal model of the radio signal is concical, I believe the actual radio signal shape is closer to a paraboloid (egg shape).

That would be a good explanation, I like it. However, it would only fit the Wikipedia and empiric data if it the egg were less than 2000 ft high - decreasing size above 1000 ft :). So I still wonder if anybody knows the exact numerical solution to this question.


text:
Is there any free source for current airline schedule data?
I am looking for a free database with complete and accurate airline schedules, especially for major European carriers.
I know there is https://openflights.org/data.html but I find the accuracy of the data very low or at least heavily outdated.
Can you point me to some other, free sources?
It can even be a website one could copy content from, not necessarily a csv or an API.
This is for academic use only. Maybe some paid sources have other policy for non commercial use?

I am currently developing a plugin for virtual airlines to pull live data, and I use the FlightAware's API which is really good in my opinion. With a little bit of php magic you can get all the schedules for your airlines for free (if you sign up for the free account) or you can pay to get access to the getAirlineSchedule query which just basically does what it says.
https://uk.flightaware.com/commercial/flightxml/
There is the website if you're interested, to get access to the free area, sign up and click the 'get prices' area and the very left option should be the free pack ;)
If you're interested in my code which I am developing, you can check it out at my github;
https://github.com/RAZERZ/PullFlightData
Good luck ;)
EDIT: You get the data in the form of json, so you can pull strings of data from there :)


text:
Why is the aiming point distance shorter in the US vs. Europe for long runways?
In essence, if you compare EGLL and KJFK (but it works for other airports too) you would see that US airports generally adhere to the rule of 1000 ft in distance between threshold and aiming point base. In Europe there usually is an additional (2nd) pair of TDZ zone markings which brings an additional 150 m to a total of 450 m between threshold and aiming point.
What is the source of this diversification and does it change how a pilot would handle final approach in two different settings? Lower flare/harder touchdowns in US?
For simplicity let’s assume we are comparing long (i.e., 3 km or more) runways only.
EGLL example: please notice that even at EGLL there is 420 m at 3 directions but 27R is 470 m.

KJFK example:

Are you able to provide a photographic comparison (from Google Maps perhaps)?

I have attached example from EGLL where same runway has different aiming point distances from TDZ.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How do ATCs choose between Tower, Approach, and Enroute facilities?
Under the FAA system, regarding the allocation to different streams for ATCs, how is this decision made? Do trainees decide early on during training which stream they'd like to work for and participate in respective training? Or do they receive a general/abstract training and are then separated among different streams for further training?
I'd like to become an ATC in the US, but can't seem to find this information anywhere. I'm wondering if tower ATCs get to finish their entire careers in towers? Or do they have to obtain radar licenses at some point and transfer/relocate to radar facilities?

As a suggestion, might be worth calling a tower close by and asking if you could get a quick tour & talk with a controller there.  Pick a time that's not too busy, and you have a good shot at getting to see the operation & chat with the controllers there.  Maybe they'd even have a recent hire who could describe their experience going through the process, and what their options look like going forward.

Or even ask when is a non-busy time to stop by! ;)

The initial assignment has been made when you're hired, and you'll be sent to either Enroute or Terminal training. The split there occurs as they're hiring to fill a class, or just sending out names to facilities to pick from, or some other factor that they keep changing. The terminal option I believe they'll say class x will get to choose between the following facilities in order of how well they did in class.  (How facilities get assigned is changed a lot, and I'm not positive how they're currently assigned).
If you go to a tower or a Tower/Tracon(up/down facility), then you'll go to the academy for the tower initial class. If you get assigned to a TRACON, you'll go to a tracon dedicated class. Enroute goes to an Enroute class. Each has their own lengths. If you're at an Tower/TRACON combined facility, you'll go through the Tower course in Oklahoma, and then go to your facility and get trained in the tower, once done there, you'll then be sent to Oklahoma again for the Radar course, and return to your facility for training in the TRACON.
A career in the US ATC system is generally what you make it. Enroute people generally stay at their centers, they don't move facilities as much, mainly as they're at the upper level facilities and at the top of the pay levels. People in the terminal environment move a lot more. In the past to move to the highest level towers, they often wanted to see a radar certification, or some other way to differentiate candidates. But things have changed recently, and I'm not sure how they're picking candidates fully now. Also you can changed tracks, from Terminal to Enroute or vice versa, but it's generally a less common move.


text:
Where inside a black box is the data storage located?
In a news article I saw this picture of a black box from a crashed A320. The article mentioned that finding the black box had lead to some disappointment due to the black box having been damaged:

This got me wondering where the actual data storage is located inside the black box. The cylindrical piece on the left looks like it is designed to be more robust than the rest of the hardware, so I am guessing that is where the data storage is located.
Are the reports of the damage exaggerated in this case? Or is any of the critical data stored in those parts of the device which have been damaged?

Which one? The FDR and the CVR are not commonly called "the black box."

@raptortech97 The article didn't specify which one. It just mentions that it is one of the two black boxes.

@raptortech97 I found another article stating that it is the CVR.

The image of the recovered "black box" is showing the Cockpit Voice Recorder (CVR). The data is stored in the cylindrical housing that was relatively undamaged in the crash.
The housing consists of a stainless steel outer shell to withstand impact forces. Beneath it is a layers of high temperature insulation to protect the data storage from post crash fire.

How did you get this picture? It says right on it DO NOT OPEN!

All I see is "uu ıvuı OPEN"

Inside the high temperature insulation is a thick layer of wax, designed to absorb lots of heat by melting.


text:
What software is used for aerodynamic wing shape optimization?
I can see lots of research articles around aerodynamic shape optimization of airfoils and wings like this MDOlab program. But all stuff like that don't seem to be available for a simple customer. Personally I've not seen where I can buy or download it. The only programs for that purpose that I've managed to find are:

Tosca Fluid (not adapted specifically for the airspace industry)
ANSYS Adjoint Solver (probably OK, don't know yet)
This Python code coupled with XFoil, but it's primitive and only for airfoils, not for wings.

Somebody know some accessible software for shape optimization of airfoils and wings for an ordinary engineer, but not for scientists or programmers?

If you follow the AIAA publication number (AIAA-2014-0567) given in the first frame of the linked video, you will find this article which explains in detail that the optimisation shown in the video was done on MACH:

These tools are components of the framework for multidisciplinary
  design optimization (MDO) of Aircraft Configurations with High
  fidelity (MACH). MACH can perform the simultaneous
  optimization of aerodynamic shape and structural sizing variables
  considering aeroelastic deflections.

If you now google for MACH, you will find this article by Gaetan Kenway which explains in detail how the software works. But this is not what you want, my impression is you need a simple to use software which can be downloaded and run within minutes.
My recommendation would be XFLR5 which incorporates the XFOIL airfoil solver and adds modules for designing and calculating the whole aircraft. YouTube has a variety of tutorials available. Is that what you want?
However, a basic understanding of aerodynamics and the possibilities and limitations of the algorithms used will be very helpful - a good engineer should be able to think both like a scientist and a programmer.

Do you know if MACH is a software for internal use only? I can't find any links to get it and no source codes.

@Bzhenko: Yes, I could also not find any link - maybe you ask the MDO lab at the University of Michigan directly? But MACH is not something simple that can be used casually - it looks more like you need to work for weeks until you get the first case running.

http://openmdao.org/ This website has an Open source tool for multidisciplinary optimization.

I would recommend the use of Aeolus ASP for aerodynamic shape optimisation.
Edit: I am not associated with the software in any way. I had found its shape optimisation features useful for an assignment at my university.

In order to avoid this post to be marked as spam, could you please clarify: -  are you associated with them? - why would you recommend that?

I am not associated with Aeolus, but their software was really useful and handy for shape optimisation for an assignment I had to do at my university

Congrats! You're one of the very few who have ever responded to that prompt! Greatly appreciated.

I'd also recommend looking at XFLR5 because that's what I see most people in the homebuilt experimental and radio controlled communities use. Specifically, most competition planes like F5D pylon racers and F3K hand launched gliders are almost all designed on XFLR5.
But XFLR5 is primarily for simulation. Verifying your "hunches" are correct and testing your tweaks. Design and optimization is still mostly done by gut feeling and educated guesses.
However, the RC community have come up with an XFoil based genetic algorithm optimizer. Check out XoptFoil (google it). You just need to give it a starting airfoil and the target characteristics you're after and let it evolve it until it gets as close as possible to your target.
Note though that AI algorithms like the genetic algorithm can sometimes give nonsense results because it's the one that fits best to the desired target result. It only means that the algorithm have managed to generate the best airfoil that has the characteristics you want in the simulated world of XFoil, not necessarily the real world. You still need to build the wing and verify.


text:
Is it possible to reach an A340's fuselage from the ground?
There is this ATC recording where an A340 pilot requests to leave the aircraft and close the fuel panel on the bottom of the fuselage, while the aircraft is on a taxiway (the request is made at 2:50). Now, here is a picture to show how to get in and out of an A340 without deploying the emergency slides and causing even more issues:

(Source: http://www.flugzeugbilder.de/show.php?id=695499 and yes, I realize this is technically a A330)
However, the picture also makes it look like it not actually possible for anyone to reach the fuselage from the ground. Is that actually the case? And if so, how would the pilot actually reach the fuselage and close the fuel panel?

@fooot I would argue not, I'm not asking how the pilot could get in and out of the airplane itself, I'm wondering how he would reach the fuselage aft of the wings.

Yes, the refuel/defuel service panel can be reached from a person standing on the ground.
From the Airbus A340-200/-300 Aircraft Characteristics - Airport and Maintenance Planning document, the height of the panel in question is just under 2 meters from the ground:

The panel is located on the lower area of the wing/body interface fairing as seen here (item 13):

As you can see in this image of an A340, there is a person standing under the front who is easily in a hand's reach from the bottom of the fuselage. So yes, the pilot could reach to the bottom of the fuselage to close that panel.

Original Image Source
Another closer view with another person (He is standing a little further away though):

Source

Damn, the perspective in the other image has really thrown me off. It looks like there would be no way to reach the fuselage.


text:
What was the earliest plane in push-pull configuration that flew or at least took off?
I am looking for the earliest plane in push-pull configuration that flew or at least took off.
I have found such planes ("Short Triple Twin" and "Short Tandem Twin") flown in 1911. So, I would be especially interested in push-pull flying machines that took off before 1911.

The Shorts S.27 was just a pusher unless you mean the Tandem Twin, are you asking about aircraft that have both pusher/tractor configurations? Like the Cessna Skymaster or just pushers?

The Wikipedia page I quoted also talks about two 1911 planes named "Short Triple Twin" and "Short Tandem Twin". Yes, am asking about planes that have a pusher-tractor configuration. I will modify the question to be more clear.

From what I can tell, the aircraft you referenced is the first flying example.

I have found a plane, that had both a pusher and a tractor propeller, which flew for the first time over Cotroceni airfield, Bucharest, Romania, on June 17, 1910. Likely there are other planes like this that flew before.

Vlaicu I plane during construction

Newspaper article about Aurel Vlaicu's first flight June 17, 1910
Source: A Vlaicu I - Wikipedia

I wonder how they found the gigantic rubber band to make it go? :)

The rubber band was a 50 hp Gnome Omega rotary engine similar to this one: https://www.youtube.com/watch?v=-UBAukXPD-0

Actually, in my studies, while working on a book about pusher aircraft, I came across this much earlier push-pull Russian aeroplane. I also have other examples of pusher and pusher-puller airplanes much earlier than 1910.
https://en.wikipedia.org/wiki/Mozhaysky%27s_airplane
Terrence Murphy

I believe the question is referring to the earliest push-pull plane that really flew in front of reliable witnesses. It is not clear whether Mozhaisky's airplane flew.

What other examples do you have?


text:
When can I descent below the MDA if the approach light system does not have red terminating bars?
Specifically, I'm a little confused about Sec 91.175(c)(3)(i) which states:

The approach light system, except that the pilot may not descend below
  100 feet above the touchdown zone elevation using the approach lights
  as a reference unless the red terminating bars or the red side row
  bars are also distinctly visible and identifiable.

From what I understand, I'm allowed to descend up to 100ft above the touch down zone elevation (TDZE) if I'm able to see and identify the red terminating bars on the approach light systems (ALS).
However, what happens when the ALS does not have the red terminating bars (for e.g. MALSR and MALSF)? Do I maintain my MDA even if I have part of the ALS in sight?

Same topic: Misunderstanding Part 91.175.

"It's important to know that not all approach lighting systems have red terminating or red side row bars. [...] the MALS [...], doesn't have them as shown in Figure 8. So, if you end up at 100 feet above the TDZE and can't see one of the first nine runway references, a missed approach is necessary. This is one reason why it's very important to know what type of approach lighting is available at the airport before you shoot the approach." (source)

You can descend down to 100ft above TDZE if you have any ALS in sight. You need an ALS with red lights (ALSF I & II) to go below that.
Red terminating bars/red side row bars help you find the threshold. Think of an ALS with red lights as being in the same category as Runway/lights/markings, Threashold/lights/markings, Touchdown Zone/lights/markings, VASI/PAPI, and REIL. Any other type of ALS (MALSR, MALSF, etc.) has the 100ft above TDZE restriction put on it when it is the only thing you can see.
@mins linked to a couple of helpful articles in the comments.


text:
Is setting elevator to certain angle equal to trimming the horizontal stabilizer?
(I was trying to understand the longitudinal stability of aircraft and how it is related to elevator)
If I pull the stick back by, say 2 inches, will it have the same affect as trimming the horizontal stabilizer to make the aircraft fly at that angle of attack?
I mean, does setting the elevator at constant 2 degree will make the aircraft swing its nose up as long as the stick is held or does it trim itself to the new angle of attack and ride steadily in its new position?

Are you asking if pulling the stick back makes the nose continuously rise until returned to the neutral position?

Yes. Or does the longitudinal stability comes  into play and levels the aircraft at, may be, reduced speed?

Somebody like Peter can answer this pretty succinctly but yes, the aircraft will slow down and fly level at a higher angle of attack, lower speed, and higher drag. If you want to initiate a sustained climb, you'd have to increase the power as well.

I expect the trim tabs to be adding some drag (no free lunch), but it would probably be small or negligible. Holding the stick back manually should be very slightly more efficient. If you are hydraulically holding the stick back, then any drag savings goes into hydraulic pump load.

Yes, both are equal for small angle changes. Exceptions do apply, especially in transsonic flow.
Both changing the stabilizer incidence and the elevator deflection will change the lift distribution between wing and tail surfaces and will trim the aircraft for a different angle of attack. Changing the incidence gives the empennage a new angle of attack while changing the deflection will change the camber (and with it the zero-lift angle of attack) and the angle of attack of the empennage. For small deflections the effect is the same; however, the change in stabilizer incidence is smaller than the elevator deflection change for the same effect in proportion to the square root of the relative elevator chord.
Say you change the stabilizer nose-down rsp. the elevator trailing edge up. The tail will produce less lift / more downforce and the aircraft pitches up. Now the angle of attack of both the wing and the tail will increase which increases lift on both until the distribution of lift between both is as before - after all, we did not change the position of the center of gravity, and the angle of attack will change until the center of pressure is exactly below or above the center of gravity again. There the aircraft finds a new equilibrium speed and will fly on in its new attitude.
Nevertheless, depending on the initial trim point, the aircraft will now climb or sink because the thrust does not match the new drag at the new trim point. The aircraft will settle at a new vertical speed, too.
Before you think that one of them would be enough: Both are needed because each is a specialist for tasks that the other would handle poorly:

The elevator moves quickly and needs small actuation forces, so it is built for manoeuvring or gust response.
The stabilizer moves slowly but can effect much higher lift changes. It is meant for retrimming during or after changes in configuration. Deflection of the lift devices on the wing will shift the center of pressure backwards, so in order to balance all lift forces, the tail now needs to produce massive downforce, something only the adjustable stabilizer is capable of.

This answer covers these aspects in more detail.

Seems like the elevator deflection would have a slightly higher drag than the stabilizer trim because of the camber. Or would it be the same since both ways would produce the same amount of lift/downforce?

@TomMcW: Not at small deflections - camber helps to create lift without shifting the stagnation point too far away from the center of the airfoil nose. Actually, an elevator is more effective than an all-flying tail and allows to use a smaller tail surface for the same control power.

@PeterKämpf, so why do all (subsonic) jets use trimmable stabilizer? Due to the larger trim range required for the larger speed difference and large moment caused by flaps?

@PeterKämpf, So I understand that with elevator up, aircraft does not just keep climbing. But rather, it finds a new equilibrium and stays level at that? (which is pretty much same as trimming horizontal stabilizer to higher angle of attack)

@user2927392: Yes, it finds a new equilibrium speed. At this speed it may fly level, climb or descent, depending on thrust. (I added "speed" - I hope this makes it more clear). It does not keep pitching up, but can still climb at the new equilibrium.

@JanHudec: The trimmable stabilizer is needed for the strong pitching moment changes when the high lift devices are deflected. They add a lot of lift aft of the neutral point of the clean configuration, which causes a strong nose-down moment. The trim range of the stabilizer is much larger in the negative range than in the positive range for exactly that reason. A second reason is a higher permissible c.g. range, but the main requirement is the flap moment.

Yes. See Chuck Yeager re man’s discovery that trim tabs don’t work once you hit supersonic. What you describe saved his life and why Mach fighters today use stabilators to trim instead of trim tabs.


text:
How can the radar range for ATC be estimated based on stated maximum radar range?
Is there a way to estimate the maximum effective range of a naval radar for air traffic control functionality, based on the radar's stated overall max range?
For instance, if a naval radar that has targeting functionality states that it can detect artillery fire at a maximum range of 75NM, is there a way to estimate its range for air traffic control purposes (e.g., a max range of 75NM translates to about a max functional range of 25NM for air traffic control?

I'm not sure this is an aviation question, but still: The radar you mean is a true radar, called primary radar on ATC jargon. These radar are not the main source for aircraft ranging in ATC. The main source is the secondary surveillance radar or SSR. SSR is barely comparable with a primary radar. Anyway the primary radar capability is dependent on its power and wavelength, and also the elevation of the target. So to allow a comparison you need to provide more elements regarding the naval radar.

You may also be interested in Radar basics

Thanks for the info, and for this Radar basics website. Both very helpful. I think I have my answer, which is that there is no easy answer without considering additional parameters.

Artillery shells are quite small compared to aircraft. It is easier to detect a non-stealth aircraft than an artillery shell. However making a general statement is difficult as there is quite some processing involved to filter out unwanted targets. You have to separate the technical capabilities of the radar hardware from the technical capabilities of the data processing. It may be that this radar detects aircraft at 100 NM, but after processing none will be displayed.


text:
What does the Airbus A340 Primary Flight Display look like during startup?
I'm developing a simulator addon and I'd like to accurately show what the A340 Primary Flight Display (PFD) shows during its startup sequence.
I'm looking for any images, photos, documents or movies that show the display from a cold and dark start until it's fully operative. That might include different states like a boot screen, self test and so on.
I can easily find information on what the PFD looks like once startup is complete, but what is displayed before that point?

Your question will probably do better if it's clearer. Try removing phrases like "or whatever" and make sure there is a clear question and other relevant details are clear. Good formatting also encourages answers.

I'm developer of such addon so i need some info from the real world. I'm in contact with pilots of A340, but they cannot provide me such informations so far. A340 cold and dark gives nothing (except simulations) - this is not so easy as it looks. By "whatever" i mean each state, which could be shown, i'm not aware sofar how they are called, so i hope that someone will be able to explain what is what.

Initially, I would like to apologize for the not-so-good quality of the pictures (there were taken into a busy enviroment).
I tried to find some vector photos from the respective manuals but I couldn't, that's why I took them by myself.
I am going to provide you with some information on each photo. It is very synoptic description in order to get the help you need for the development of your stuff, and to cover this question.
In case that you need any further technical information please open another question.

1) Immediately after provide the a/c with power.

2) After 40s

3) After approximately 50s and before initialization of the ADIRS (which is taking place at cockpit preparation after the preliminary cockpit preparation checklist.)

4) Approximately 15s after the startup of the ADIRS, and during the "IR alignment in progress." (info* on ECAM)

5) During IR alignment in progress. (Only here the FDs are by default ON when the a/c is powering up, and the red FD symbol on the PFD during alignment is flashing, then manually FDs are switched off.)

6) After IR alignment and before FMGS PERF PAGE preparation, (and FDs still are OFF).

7) FDs are ON, FMGS preparation at PERF PAGE not completed yet, and ENGINES are OFF.

8) FMGS PERF PAGE data inserted, FDs ON, ENGINES OFF.

Welcome! One cannot dream of a better answer.

Yeah mins, you are right - no better answer. Above material is just amazing, real treasure for me :). Big Thank You Emmanuel!

My pleasure Robert...


text:
How is the battery power on the Airbus A340's electric system switched?
On the electric panel of the Airbus A340 there are three battery buttons (BAT 1, BAT 2 and APU BAT, indicated by (3) and (4) in the diagram) controlling battery charge limiters. When the aircraft is on the ground, below 50kts and batteries are the only power sources (as FCOM states) batteries 1 and 2 should be connected to the DC-Battery bus (DC_BAT_BUS) and the DC-Essential bus (DC_ESS_BUS).

source: Airbus A340 FCOM 1.24.20 P1 REV08
Should both of battery buttons 1 and 2 be pressed to Auto mode to have these connections? Or it is possible to connect battery 1 separately from 2 to DC_BAT_BUS? Seems that both buttons should be pressed to have such connection to DC_ESS_BUS, but for DC_BAT_BUS it is not so obvious.

From A340 FCOM 1.24.20 P2 (REV 8):

BAT 1 (2) pb sw
Controls the operation of the corresponding Battery Charge Limiter
AUTO:
The Battery Charge Limiter controls automatically the connection
  and the disconnection of the corresponding battery tot the DC BAT BUS
  by closing and opening of the battery line contactor.

The batteries
  are connected to the DC BAT BUS in the following cases:

Battery voltage below 26.5 Volts (battery charge). The charging cycle ends when battery charge current goes below 4 Amperes (for 10 seconds on ground 30 minutes is flight)
On the
  ground (with speed below 50 knots) when batteries only are supplying
  the aircraft.

My understanding is that for the DC BAT BUS this means when a button is set to AUTO the corresponding battery is connected when that battery needs to be charged or:

The aircraft has a speed below 50 knots AND
The only power source is batteries (i.e. no generators, APU or external power supply are connected to the electrical network)

A note further down mentions that the batteries are disconnected  when the voltage drops below 23 Volts for more than 16 seconds, in order to protect the battery from discharging completely.
For the DC ESS BUS it states:

The batteries are connected to the DC ESS BUS when batteries only are
  supplying

in flight
on the ground (speed below 50 knots) provided they are
  both selected auto

That clearly states that both push button switches need to be set to AUTO in order for the DC ESS BUS to be powered from the batteries on the ground.

(Sorry for mess, have problems with formatting message, help needed here)
FCOM 1.24.10 P19 (REV10) states (regarding DC busses):
ON GROUND BATTERIES ONLY
Provided they are both selected AUTO, the batteries supply:

the DC ESS BUS,
the DC BAT BUS,
the DC LAND RECOVERY

So maybe it is like this: when battery is charging it could be connected to DC BAT BUS independently from the other one, but when they are supplying this bus, both push buttons need to set to Auto?

@Robert I think they can power the DC BAT BUS independently as well. Do you know any systems that are powered from the DC BAT BUS?

Maybe you are right, i could consider something like that for my purposes. There seems to be some systems powered from DC BAT BUS, probe heaters, fire and smoke detectors and some engine control stuff as well.


text:
What would happen if I had a type rating for an Airbus A320 and applied for an airline that has an A320 and other aircraft?
Let's say I have a type rating for an Airbus A320 and applied for lets say delta. So we know that Delta has an Airbus A320, Airbus A330, Boeing 737, Boeing 777, etc. Suppose I have an Airbus A320 type rating and I applied and passed the interview and everything, will they automatically assign me to the Airbus A320 considering I already have an Airbus A320 type rating , or not? (By Airbus A320, I mean the Airbus A320 family which include the A318 A319, A320, A320 neo, A321, A321neo)

That depends on the airline. They may be looking for pilots in one specific type, or they may let the applicant choose. It is the same question as "I know C#, I applied at a company that uses C#, C++ and PHP, which team will they assign me to?"

They have to put you through their training regardless of what ratings or how many ratings you have.  You would likely be assigned to where they needed pilots.  Your 320 type (assuming it's just a type rating and you have no "real" flight time) may be a factor in the planning process but it by no means locks you into a 320 series.

No. You'd take the same initial course as everybody else, learning that airline's procedures & checklists for that aircraft.  Having a type rating shows the hiring people that you're able to pass the training course & checkride for that level of aircraft, and that's good to have. But beyond making the aircraft systems part of the syllabus easier for you, having the type won't change your training.
It also probably won't affect which aircaft you initially get. Those are based on where the airline needs pilots, and then (typically) on some sort of bid process. The airline presumably expects all its new pilots to be able to complete whichever training course they get, so your type and/or prior experience is unlikely to drive your initial assignment.
For a new, small airline in need of hiring captains off the street, things might well be different.

No, you would begin as an entry level FO with Delta.  For that airline it would probably be the MD88 airplane.
If you only have a type rating, in their eyes you only have enough knowledge to be dangerous.  They are probably going to want real world PIC/SIC jet time in addition on the order of 500-1000 hours of it, in addition to night an instrument time.  I've never heard of the majors demanding a specific type rating to new pilots as they will train them to operate their aircraft the way they want.


text:
How does the U.S. Overflight Fee system work?
After going through the Overflight Fees on FAA.GOV, the following is clear and self-explanatory:

Exact fees
Method of Payment (online, via Pay.gov as mentioned on the page).

What's not clear to me is the following:

The FAA charges overflight fees to operators of aircraft that fly in
  U.S.-controlled airspace, but neither take off nor land in the United
  States.

Does this mean that international flights that land at any airport within the U.S. are not liable for overflight fees, and that they're only liable to pay the other fees such as airport charges etc.?
How is the invoice/bill delivered to the responsible party? I
believe airlines/commuters have accounts that get billed, but what
about private jet owners?
What would be the circumstances if, say a private jet owner/operator
departs from Canada, lands in Mexico and doesn't pay the invoice?
What if such a trip is made once a month for a long period of time
without paying the due fees. Does that jet "not get permission" to
enter U.S. Controlled Airspace?

://www.oig.dot.gov/library-item/36135 Report by the GAO recently on this topic

Correct. Some countries charge overflight fees regardless of whether you land or not. In the US, overflight fees are charged per 100 nm. You can find the exact fees for 2017, 2018 and 2019 here. The fees can be paid online, and the FAA is pretty modern when it comes to this; it accepts ACH transfers from a US bank account, Amazon account, Dwolla account, PayPal and Debit or credit card.
The aircraft has to identify itself. The flight plan tells the FAA who you are. They look you up in the registry of the country in which your aircraft appears and send you the bill.
Unpaid fees accrue interest, and can result in the aircraft being denied entry into US airspace or impounded if it does happen to land at a US airport. The FAA can also put liens on the aircraft in the country of registration, which would have to be paid before the aircraft registration changes hands.


text:
What are the consequences of flying GA without a license (certificate)?
As far as I can tell, in the U.S., 49 USC 46317(a) makes flying without a proper certificate a crime punishable by fine and/or imprisonment.  However, the FAA is a regulatory agency, which means it can only assess civil penalties (e.g., civil fines or revocation of certificates).
In practice I've heard (and would expect) the FAA gets quite exercised over "airmen" found to be carrying passengers for hire without current and proper certificates.
What I'm wondering is whether individuals have ever been, or are routinely, subject to any scrutiny or regulatory or prosecutorial action if they fly without certificates and don't commit any other egregious violations of FAA regulations?  E.g., if you only fly registered aircraft for your own amusement, and you never break a serious airspace rule, but you never get an FAA certificate, could you expect to go your whole life without any trouble from the FAA?  If not, what sort of trouble might you expect and how would you get into it?
And has anyone ever faced criminal prosecution for flying without proper certificates who did not also commit a gross violation of safety while operating an aircraft for hire, or some other felony (e.g., smuggling)?

Some estimates indicate that up to half of all pilots in Alaska don't have any kind of license..

Sentenced for Flying Without a License

@mins - Good find.  But I wonder if the triggering circumstance was that he was flying an unregistered plane ... and how air traffic control would have known it wasn't registered?  (Also, he had previously falsified applications for certificates, and he is "owner of two aircraft parts/salvage businesses," so this may have been the equivalent of finally nabbing Capone for tax evasion, or a scofflaw for jaywalking?)

You are right, just a track to follow, there are many cases.

@mins - Wow, excellent resource!  I wonder if somebody is familiar enough with these to deduce customs or practices: E.g., all reported "sentencings* I've browsed seem to be associated with other infractions like operating unregistered aircraft.  Meanwhile, everywhere I've checked this general question I seem to find that mention that a majority of Alaska pilots have no certificates at all.

Seems TN may have a state law being enforced in that case (as well as others).

First, if you fly privately without a license can you avoid trouble with the FAA? Yes, if you don't attract attention to yourself.
It's essentially the same as driving a car without a license or insurance: it happens because some people just don't see why they should have to get a license, and it's possible because no one regularly checks every car and every driver. Anecdotally, there are plenty of pilot stories about unlicensed pilots in rural, remote areas who fly out of private strips or small, uncontrolled airports. Alaska in particular is notorious: I've heard the 'joke' several times that the FAA used to have the goal of getting at least 50% of Alaskan pilots certificated.
Second, if you do get caught by the FAA or by law enforcement, what happens? As you said, the FAA can revoke your certificate but state or federal officials can go after you with criminal charges. This is from the criminal indictment of someone who was accused of lying about his pilot's and mechanic's certificates:

At sentencing he faces a maximum of five years in prison and a
\$250,000 fine for each of the two criminal counts of making false
statements to the FAA, and a maximum of three years in prison and a
\$250,000 fine for each of the three counts of flying without proper
authorization.

He pled guilty and was sentenced to 2 months imprisonment and a $5000 fine. @mins found another example that resulted in a prison sentence.
Finally, there is one legal way to fly in the US without a license: fly an ultralight under part 103.

For the first case: "60 days incarceration, three years of probation, and a $5,000 fine [...] also ordered to sell his airplane and not enter an airport, unless [...] as a passenger, for three years"

Only prosecution in UK recently was in 2011, guilty of being pilot in command on 3 occasions, once on UK registered, twice on US registered passenger aircraft.  Fined £4500 plus £1100 costs.

@user23614 still cheaper than flight training.

As it was explained to me by an unlicensed pilot and an FAA inspector having lunch in rural Alaska, the punishment if any is determined by how serious the infraction. If you are caught like this guy was, having a quaint conversation along with a sandwich, probably nothing. If you were doing something that endangered only yourself, the FAA will insist you get certified before operating the aircraft. If you endanger others the penalties get more severe. Etc etc. it also depends on the mood of the official and your response to his inquiry. long and short of it, could walk away with a snicker and a warning, might get the book thrown at you.


text:
Are there any rules requiring hands/feet on the controls at all times?
Are there rules that require one of the pilots in a large commercial aircraft to have positive physical control of the yoke/joystick at all times?
And the same question for the rudder actuators, if any (pedals)?

None that I know of.  There is someone responsible for flying the aircraft at all times, but nothing specifically requiring them to have them in their physical possession.

You may fly the plane for a long period without touching the yoke and pedals. Airliners are equipped with autopilot and the pilot flying the aircraft set up and monitor the autopilot.

Now that time has gone by, this is where this question came from. In another question, someone commented about since how the side-stick airbus' have no column in front of the pilots, there is a tray-table. When I read that, I pictured mid-atlantic/pacific, both pilot's hunched over doing crossword puzzles, shoes off and feet curled up under them. :)

Doing my PPL, one thing that always struck me is how much of the time I spent with my hands/feet off the controls compared to driving a car. I basically never touched the thing between fiddling with maps/mics/sunglasses/knee boards/writing clearences/recalculating routes. Learning to fly is basically an exercise in multitasking

There is nothing I can find in the FARs requiring that a pilot keep their hands and feet on the controls at all times.
Such a requirement would be impractical and dangerous in many situations (such as when writing down a clearance in the air: For most people if you keep your hands on the controls while writing you will have a tendency to push, pull, or twist them, resulting in unintended attitude changes).

The most relevant sections of Part 91 would be 91.3 and 91.13:
14 CFR 91.3 (FAR 91.3) says:

§91.3   Responsibility and authority of the pilot in command.
  (a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.
  . . . .

and 14 CFR 91.13 (FAR 91.13) says:

§91.13   Careless or reckless operation.
  (a) Aircraft operations for the purpose of air navigation.
   No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another.
(b) Aircraft operations other than for the purpose of air navigation.
  No person may operate an aircraft, other than for the purpose of air navigation, on any part of the surface of an airport used by aircraft for air commerce (including areas used by those aircraft for receiving or discharging persons or cargo), in a careless or reckless manner so as to endanger the life or property of another.

So basically it's perfectly legal for a pilot to fly with their arms crossed and their feet flat on the floor, even without an autopilot, as long as the pilot in command remains able to exercise operational control of the aircraft as required to ensure the flight remains safe and legal, and as long as they are not acting in a "careless or reckless manner" (like letting their altitude wander all over the place while sitting with their arms crossed).

No. What is required by FAA is that one of the two pilots (the captain or first officer) must be the "pilot flying", and this pilot has primary responsibility for maintaining control of the aircraft at the time. The other pilot, the "pilot not flying", may assist the pilot flying by performing secondary tasks such as communication or navigation, or he/she may use the lav, have a snack/drink, read (the FAA does not prohibit reading materials not directly related to the job, but some companies do), do puzzles (ditto), etc.
Neither of these pilots are required to have hands on stick/yoke/throttle and feet on rudder pedals at all times. First off, it's redundant for most of the flight; when cruising, the plane is on autopilot, which will keep the wings level and the plane on a designated course. Second, airliners (in fact, most civilian fixed-wing aircraft) are much more stable in flight than helicopters, which do require someone to have their hands on the cyclic stick at all times to keep the helicopter "on top of" the lift vector of its rotors. So, even if the autopilot is disengaged, in normal, calm conditions the plane will almost fly itself, requiring only small corrections for turbulence. In any case, a "ham-fist" or "lead foot" on the controls is a common student mistake, much like in driving; pilots usually try to heed Han Solo's advice: "fly casual".

Helicopters are unstable, period. Without a stability augmentation system, a heli will be in an unusual attitude in half a second if you take your hands off the cyclic. That being said, many helis do have SAS, and it is required for IFR, so those helis don't always need a hand in the cyclic.

I thought the PIC always had primary responsibility for the aircraft, even if they were the PNF?

@cpast - Parallel, slightly different. The captain, as PIC, is the ultimate authority on board and ultimately responsible for the safety of the plane and its passengers. He does not always have or need direct control over the aircraft's flight systems and thus responsibility for its flight path and operation, which is the idea I was trying to convey. He may also delegate or defer any of his powers as captain aboard the aircraft to his First Officer or any other crewmember.

Nope. Sometimes they just let go and yell, "Look Ma! No hands!" into the local traffic channel. Just kidding.
There may be a slight disconnect here in how you think about pilots and the law. The average (non-pilot) person imagines that pilots are robotic servants that must obey all kinds of laws and regulations designed to "protect" passengers and slavishly follow orders from (non-pilot) FAA controllers. That is not how it works.
In the sky, the pilots are the bosses. ATC and the laws are there to help the pilots do their job better, not boss them around and force them to them to do things they don't want to do.

I don't think he imagines that pilots are robotic servants. It was a genuine question that deserves better than a flip answer.

You play it off as a joke, but on calm days I frequently cross my arms and put my feet on the floor to demonstrate to passengers that yes, the aircraft will continue to fly perfectly fine for quite a while without my help. (This demonstration is somewhat less effective in turbulence or when there are gusty winds though.)

@voretaq7 Let me know which plane you fly and I will take next one :)


text:
Why are there so many different propeller shapes?
While doing an image search, I found these images of propellers:

and

Some appear to be straight-ish on the leading edge and curved on the trailing, some curved on the leading edge and straght-ish on the trailing, and symmetrically curved and some pretty squared off.
It seems like, well, a propeller is a propeller. They all need to push the air back in a way as to propel (hence the name?) the plane forward.
Wouldn't there be a mathmatically 'best' design?

The best design depends on what your goal is. This changes with operating conditions:
Best power/thrust ratio
For lightly loaded propellers this would be minimum induced loss. These are the propellers on human-powered aircraft, windmills or motor gliders. Minimum induced loss is achieved by distributing circulation elliptically across the propeller disc, and a typical consequence is a small chord near the tips and a low number of propeller blades. If you want to research this more, I recommend to play around with XRotor by Mark Drela (and maybe reading this). Mark used it to design the MLE (below, NASA photo EC87-0014-8) and Dedalus propeller.

Maximum thrust at high speed
Highly loaded propellers, which can be found on large turboprop aircraft, are less concerned with induced loss, but need to put out as much thrust as possible with a limited prop area. The diameter is restricted to limit tip speeds, and the tips typically are mildly supersonic. To limit the suction peaks on the blades, the local lift coefficient needs to be low, which is achieved by increasing chord and the number of blades. Increasingly, now tip sweep is also used, but this drives up the torsional loads on the blades and leads to warpage in operation. An extreme example is the P-27 prop on the D-27 turboshaft of the An-70 transport (below, picture by Marina Lystseva).

Ship propellers
They operate in a medium which is 800 times denser than air, and the main concern is to avoid cavitation. This again means to limit suction peaks and leads to very high blade chords. To limit draft, ship propellers need to have extremely small diameters.

Submarine propellers
For submarines, add  minimum noise emission to the design goals. Minimum draft is not a concern, so the propeller blades are less stubby. Their sweep distributes the cutting through the wake of the rudders over time, which helps a lot to reduce noise.

The fancy shapes of some model aircraft propellers have more to do with marketing or unscientific voodoo beliefs by some hobbyists. Generally, a straight shape works best.

I was going to also ask about helicopter blades, like the Huey and Blackhawk, which tend to be straight and square. I didn't know whether that was worth a separate question though.

helicopters would fall in the first category (max thrust for the power)

Re: Submarine propellers, there's actually a scale model of one on display at the Smithsonian Institution. They went through a lot of trouble to get the thing, too.

"For obvious reasons, I cannot post a submarine propeller photo here"
This is not obvious. Why?

@Vortico: Well, I could post an old photo. State-of-the-art submarine propellers are top secret. They are even hung with covers when the boat is in the dry dock, so satellite photos wouldn't reveal anything.

Article at this link has a photo of an uncovered sub in drydock, visible on Bing Maps, and comments on the controversy that happened when this image was discovered.

@CGCampbell: Helicopter blades have extreme aspect ratios and, as a consequence, too little torsional stiffness to optimize lift distribution over their radius. They use reflex airfoils to zero the torsion moment and use more or less the same chord and angle of attack over the radius. This is not efficient for hover, but works reasonably well in forward flight.

@PeterKämpf Peter, if I ask a new question specifically about helicopter blades, such as those on a Bell Huey, you could answer that in a way as to explain the above paragraph? As some say, you used all English words, and I understand most of them, but the total is greek.

@CGCampbell: I'll try my best!

@RossPresser 's link is dead and 404s, but is on the wayback machine: https://web.archive.org/web/20150423005349/http://lewis.armscontrolwonk.com/archive/1626/secret-screws

A couple of extra points for piston engine aircraft:
The size and amount of propeller blades mostly depends on the power output of the engine. A giant prop on a tiny engine won't be good, because it consumes too much energy just to spin it. Conversely, a small prop on a big engine would waste a lot of the engine output, as the prop would overspeed before the engine reached peak performance.
Matching prop size to engine is one of the challenges for designers. As mentioned in the previous answer, it depends on what the aircraft will be used for.
Also, most propellers do not actually move the aircraft by 'pushing' the air behind. If that were the case it would not make any sense to have them on the leading edge of the wing or on the nose - you should place them with clear air behind. The propeller is actually an aerofoil, producing lift using the same principle as a wing. Negative pressure is created on the 'upward' side of the prop, so the propeller 'pulls' the aircraft forward.

A wing also pushes air down. Looking at the pressure is describing the same physical process in a different way. So propellers do push air behind, and they do this by accelerating it by means of suction on the forward-facing part of the blade. And pusher propellers are indeed the more efficient way of mounting a prop, but have problems of their own.

Ben, in the AN-70 picture above, how do the second sets of props not interfere with the first? I know, you said most. I'm only an enthusiast, to me, a lot of flying is magic, but I'm learning. Talking about how a piston-driven prop works is somewhat akin to how electricity works.... hole flow? or electron flow?

Unfortunately I am by no means an expert - I am still learning every day. The AN-70 has a different type of engine known as a Propfan, which I understand to be almost a hybrid between a turbofan and a turboprop engine. I could therefore make a guess as to how the two props interact but I think I will leave that to the experts :)


text:
Is there a way to obtain real-time METAR data?
I know that METAR data are available at hourly intervals from the US National Oceanic and Atmospheric Administration (see e.g. the report for Karpathos Airport, Greece ).  However, I would have thought that at the age of the internet it would have been possible to obtain (near) real-time data regarding an airport's weather.  Is such a service available?  Is there a better (more frequently updated) internet-accessible source for global METAR data than NOAA?

METARs aren't meant to be real time because of how they are used, if you want real time data you'll have to look at other sources.

A METAR is a prepared report (admittedly usually automated), not a snapshot of single data points. They average/aggregate data over the reporting period to remove extreme or very temporary readings. And METARs also provide SPECI reports if something significant changes in between the regular updates, so there's no reason to think that a 45 minute old METAR is completely inaccurate. Having said that, in theory I suppose you could generate on-demand METARs using rolling data, but I don't know if they exist. You might ask on earthscience.SE too if you don't get a good answer here.

Actually, I believe the METAR's published by NOAA are updated on their server quite frequently (certainly more than once ever hour). However, in most countries, a METAR is only published every 30 or 60 minutes. So it is not a matter of NOAA not being up to date, it is a matter of METAR's not being published more frequently.

@Pondlife The average/aggregate vs snapshot distinction is important, thank you!

@J. Hougaard You write that METARs are updated on their server quite frequently.  Are these servers accessible over the internet?

Sure. I usually access them like this: ftp://tgftp.nws.noaa.gov/data/observations/metar/stations/ICAO.TXT (replace ICAO with the ICAO designator of the airport)

Thank you!  That' the one I also use. They still look hourly to me. For example, it's now 06:35 UTC but the JFK METAR ftp://tgftp.nws.noaa.gov/data/observations/metar/stations/KJFK.TXT is still for 05:55 KJFK 050551Z 23007KT 10SM FEW013 SCT250 21/19 A3009 RMK AO2 SLP187 T02110189 58004 $

That's because KJFK METAR's are only issued once every hour! The database is up to date. A METAR is only published by the airport once every hour (except in the case of sudden weather changes). There is nothing wrong here - that is simply how METAR's work.

This is a matter of time before automated weather stations broadcast live because that's not difficult. They could broadcast averaged data. But is there a need, for a pilot, to have instantaneous data for an airport distant of 100 or 500 NM? They would be more interested by the forecaster briefing on the weather expected at the time they will be there.

You might know this already, but if you want to get an AWOS/ASOS report minute by minute, you can call most of the automated sites. In the US the phone number is listed in the A/FD.

is correct.  However, if you tie up a line for a long time other pilots won't be too happy not getting current weather.

Thank you!  I was looking for internet-accessible data, but this suggestion may be useful to others.

As @DiomidisSpinellis says, it doesn't answer the question

Although METARs don't provide real-time weather, you can programmatically obtain the current METAR using the ADDS Text Data Server
Here's a sample result for KDEN:
http://www.aviationweather.gov/adds/dataserver_current/httpparam?dataSource=metars&requestType=retrieve&format=csv&stationString=KDEN&hoursBeforeNow=1

KDEN 061653Z 31004KT 10SM BKN025 OVC120 22/14 A3014 RMK AO2 SLP134 T02220144,KDEN,2016-08-06T16:53:00Z,39.85,-104.65,22.2,14.4,310,4,,10.0,30.138779,1013.4,,,TRUE,,,,,,,BKN,2500,OVC,12000,,,,,MVFR,,,,,,,,,,,,METAR,1640.0

Thank you.  That's still the hourly METAR, but it's useful to know.

METARS are by definition hourly, except SPECIs


text:
Are ground crews at danger for radiation from WX radar?
I am under the impression that the radiation from a weather radar on the nose/wing of aircraft can cause enough radiation to render ground workers sterile/cause cellular damage if the pilot forgets to turn off the radar.
I know most pilots follow a checklist and probably turn it off...but what if one didn't turn it off and a person was marshalling the plane in standing close to the nose of the aircraft?

We had rampers complain of burning sensations from time to time. Management concluded that certain pilots were leaving their radar on all the way through shutdown. Stands to reason as the radome was about face level and we were marshalled to within a few feet of the rampers.

@RonBeyer I don't think this is an exact duplicate. The suggested dupe is primarily concerned about regulations. This is more concerned about the harmful effects of not following rules/regs.

You may be mistaking electromagnetic radiation from radar with atomic radiation that originates in atomic nuclei.  Radar waves are long wavelength photons.  Physical effects would be similar to microwave oven radiation, which, as already noted, can cause tissue warming.  Atomic radiation is bits of atomic nuclei which can cause all sorts of tissue damage, including DNA mutations and serious long term health damage.  They are not the same thing.

I agree with @Notts90